Death Rate In New-Onset Diabetes Higher In Those With Normal BMI

A recent study has found that, of people who have been newly diagnosed with diabetes, those with a normal body mass index (BMI) experience a higher mortality rate than those who are overweight.

The Northwestern University study, published in the August 7 issue of the Journal of the American Medical Association, found that the total of non-cardiovascular mortality rate was significantly higher in normal BMI diabetics.

“Type 2 diabetes in normal-weight adults is an understudied representation of the metabolically obese normal-weight phenotype that has become increasingly common over time. It is not known whether the ‘obesity paradox’ that has been observed in chronic diseases such as heart failure, chronic kidney disease, and hypertension extends to adults who are normal weight at the time of incident diabetes,” according to background information in the article.

Experts know that being overweight is a risk factor for developing the blood sugar disease, but the researchers expect other factors such as family history, ethnicity and age also plays a role.

“It could be that this is a very unique subset of the population who are at a particularly high risk for mortality and diabetes, and it is possible that genetics is a factor with these individuals,” said study lead author Mercedes R. Carnethon, associate professor of preventive medicine at Northwestern University Feinberg School of Medicine.

Carnethon and colleagues conducted the study to compare the mortality rates between participants with normal BMI and those who are overweight or obese at the time of diagnosis of diabetes. The researchers gleaned data from a pooled analysis of 5 studies with a total of 2,625 participants with new diabetes. The studies included men and women over the age of 40 who developed incident diabetes based on fasting glucose of 126 mg/dL or greater or newly initiated diabetes medication and who had concurrent measurements of body mass index (BMI).

Normal weight BMI is considered to be 18.5 to 24.99. Scores of 25 or higher are considered overweight/obese.

The proportion of adults who were at normal weight at the time of onset ranged from 9 to 21 percent. During follow-up, 449 participants died: 178 from cardiovascular causes and 253 from non-cardiovascular causes; 18 were unidentified.

After adjusting for certain variables, the researchers found that participants with normal BMI experienced a significantly greater mortality and non-cardiovascular mortality. Cardiovascular mortality was also elevated, but the association was not statistically significant.

“These findings are relevant to segments of the US population, including older adults and nonwhite persons (e.g., Asian, black), who are more likely to experience normal-weight diabetes,” noted Carnethon.

“Many times physicians don’t expect that normal-weight people have diabetes when it is quite possible that they do and could be at a high risk of mortality, particularly if they are older adults or members of a minority group,” Carnethon said. “If you are of a normal weight and have new-onset diabetes, talk to your doctor about controlling your health risks, including cardiovascular risk factors.”

The researchers noted that mechanisms to explain the association are unknown. “However, previous research suggests that normal-weight persons with diabetes have a different genetic profile than overweight or obese persons with diabetes. If those same genetic variants that predispose to diabetes are associated with other illnesses, these individuals may be ‘genetically loaded’ toward experiencing higher mortality.”

They acknowledge that further testing is needed and should focus on genetic factors and other plausible mechanisms that cause normal BMI diabetics to be at much higher increased risk of mortality.

“This could be a wake-up call for timely prevention and management to reduce adverse outcomes in all patients with type 2 diabetes, particularly in those metabolically obese normal-weight at diagnosis, who may have a false sense of protection because they are not overweight or obese.”